1. Field of Invention
The invention is directed to gravel packs in oil and gas wells and, in particular, to downhole tools comprising screens for insertion into the gravel pack completions in wellbores.
2. Description of Art
In completing wells having production or injection zones which lie adjacent to incompetent formations formed from unconsolidated matrixes such as loose sandstone, or which lie adjacent formations that have been hydraulically-fractured and propped such as through fracturing processes, sand control problems often arise during the operational life of the well. These sand control problems are encountered when large volumes of sand and/or other particulate material such as backflow of proppants from a hydraulically-fractured formation dislodge from the formation and become entrained in the formation fluids and are produced therewith into the wellbore. These produced materials have an adverse effect on the operation of the well because they can cause erosion and plugging of the well equipment which, in turn, leads to high maintenance costs and considerable downtime of the well.
One technique for controlling sand production in a wellbore is referred to as “gravel packing” or forming a “gravel pack completion.” In general, a gravel pack completion comprises a screen, such as a fluid-permeable liner, a perforated liner, a slotted liner, a pre-packed screen, that is disposed within an open-hole or cased wellbore adjacent the incompetent or fractured zone and is surrounded by aggregate or particulate material collectively referred to as “gravel.” As known in the art, the gravel particles are sized to block or filter out the formation particulates that may become entrained in the produced fluids, while the openings in the screen are sized to block the gravel from flowing into the screen.
One method for installing a typical gravel pack completion in a wellbore involves placing the gravel in the wellbore first and then driving, rotating, or washing the screen into the gravel to form the gravel pack. To assist in installing the screen in gravel disposed in a wellbore, the liner may include one or more auger blades, referred to herein as an “auger-flighted screen.”